The forces killed Ezequiel Cardenas Guillen, also known as Tony Storm, in an hours-long gunbattle Friday in the border city of Matamoros, across from the U.S. city of Brownsville, Texas.

Mexican officials say three gunmen and two members of the security forces were also killed during the firefight.

A Matamoros newspaper, El Expreso, says one of its reporters also died in the shootout.

Cardenas was one of Mexico's most wanted drug gang leaders.

Mexican authorities had offered a $2 million reward for information leading to his arrest and capture, while the U.S. had a $5 million bounty on Cardenas.

He was considered a key smuggler of marijuana and cocaine into the U.S.

Cardenas took over the leadership role in the Gulf cartel after the 2003 capture of his brother Osiel Cardenas Guillen, a former leader of the drug gang, who was later extradited to the United States.

Mexican military forces have been engaged in a brutal struggle against the country's violent drug cartels. Nearly 30,000 people have been killed in Mexico's drug war since President Felipe Calderon took office in late 2006 and began cracking down on the cartels.